Temperature stability of sputtered niobium–oxide films

Abstract

The effect of annealing temperature on the structural and optical properties of sputtered niobium–oxide films has been investigated. The temperature dependence of structure, density, and optical constants has been studied by Rutherford backscattering, x-ray diffraction, x-ray reflection, optical spectroscopy, and variable angle spectroscopic ellipsometry techniques. Rutherford backscattering measurements show no variation in the stoichiometry of the films upon annealing of amorphous Nb2O5 films, while amorphous NbO is oxidized to Nb2O5. X-ray diffraction studies show that as-deposited films are amorphous and only crystallize at around 500 °C. X-ray reflectivity studies reveal a continuous increase of film density with increasing annealing temperature. Optical spectroscopy and spectroscopic ellipsometry confirm that the refractive index n and the band gap Eg increase upon increasing annealing temperature. The variation of the refractive index with density of the niobium–oxide films is observed to follow the Clausius–Mossotti relation and the molecular electronic polarizability has been deduced from the straight line fit of Lorentz–Lorentz law.

Thermal Stability of Lead Oxide Films Prepared by Reactive DC Magnetron Sputtering

“…10 for different lead oxide samples. Comparable results have recently been reported for TiO 2 [15] and Nb 2 O 5 [16,17] films. Nevertheless, to determine the thickness and density variations upon annealing we have also attempted X-ray reflectivity (XRR) studies.…”

Electrochemical Energy Storage Applications of CVD Grown Niobium Oxide Thin Films

“…Recent reports include the integration of Nb2O5 in electrode materials in supercapacitor applications, which has resulted in excellent performances ascribed to the pseudocapacitance effect involved. [13][14][15] However, the niobium-oxygen system is particularly complex, as narrow deviations from the exact stoichiometry in Nb2O5 strongly affect the physical properties of the material. For instance, a small oxygen deficiency leads to the transition from insulating to n-type semiconducting behavior 9 .…”

“…For instance, a small oxygen deficiency leads to the transition from insulating to n-type semiconducting behavior 9 . Niobium oxide films have been prepared by different methods including magnetron sputtering 15 , electrodeposition and anodization 16 , thermal oxidation 17 , sol-gel methods [18][19][20][21][22] , chemical vapor deposition (CVD) 23 or atomic layer epitaxy 24 . One-dimensional nanostructures typically exhibit enhanced charge transport properties due to their anisotropy and thus are very interesting from the device point of view.…”

Thermally activated crystallization of Nb2O5 grown on Pt electrode

“…Among the niobium oxides, Nb 2 O 5 is the most stable phase from the thermodynamic point of view, because it exhibits the lowest free energy of formation [12,13]. Still, two low temperature modifications of Nb 2 O 5 were reported by Schäffer et al [14], who described one of them as tetragonal TT-Nb 2 O 5 and the other as orthorhombic T-Nb 2 O 5 .…”